A research team led by Prof. MAO Donghai from the Institute of Subtropical Agriculture of the Chinese Academy of Sciences has uncovered the molecular mechanism by which the auxin efflux transporter HAN2/OsABCB5 modulates chilling tolerance in rice via the auxin signaling pathway. 

The findings were published in Nature Communication.

Rice, which originates from tropical and subtropical regions, is highly sensitive to chilling stress during its growth stages. As global climate change intensifies, extreme low-temperature events are occurring more frequently. Therefore, identifying genes associated with chilling tolerance and elucidating their molecular mechanisms are essential for enhancing rice yield and stability under such adverse conditions. However, the chilling-tolerance genes currently identified from natural populations remain limited.

Using forward genetics approaches, the research team cloned a chilling-tolerance quantitative trait locus (QTL), HAN2, from temperate japonica rice. HAN2 encodes an auxin efflux transporter (OsABCB5) that negatively regulates chilling tolerance via the auxin-mediated "OsARF24-OsMAP1/OsMPK3" signaling pathway. 

During rice domestication, HAN2 diverged between indica and temperate japonica varieties. In temperate japonica rice, a Copia retrotransposon insertion downstream of HAN2 reduces its expression through epigenetic modifications, thereby enhancing chilling tolerance and enabling adaptation to temperate climates.

This study advances our understanding of the adaptive mechanisms driving the northward expansion of temperate japonica rice and offers valuable genetic resources and theoretical foundation for bolstering rice resilience in a changing climate.

The HAN2 gene in rice facilitates the adaptation of japonica rice to temperate climates (Image by CUI Yanchun)

A model of chilling tolerance adaptation mediated by the rice gene HAN2 (Image by CUI Yanchun)